High-performance Cross-linked Anion Exchange Membranes Based on Rigid Poly(crown ether) and Flexible Quaternary Ammonium Poly(vinyl alcohol) for Fuel Cells

Abstract

As the core component of anion exchange membrane fuel cells (AEMFCs), anion exchange membranes (AEMs) have long faced issues such as low conductivity and poor alkaline resistance. Therefore, the selection of appropriate polymer backbones and cationic functional groups is crucial for enhancing the conductivity and alkaline stability of AEMs. In this study, rigid poly(crown ether) (B-C) and flexible quaternary ammonium Poly(vinyl alcohol) (QPVA) were interconnected using glutaraldehyde as the crosslinker to fabricate high-performance AEMs (QPVA_1-X%-(B-C)_X%). Flexible QPVA, by virtue of its hydrophilic nature, exhibits remarkable membrane-forming capabilities and effectively facilitates OH⁻ ion conduction. Rigid B-C plays a crucial role in augmenting both the electrical conductivity and alkaline stability of the membranes. Moreover, the cross-linked networks serve to enhance the compatibility between QPVA and B-C, thereby restricting swelling phenomena and further bolstering the alkaline stability of the composite materials. The results indicate that the conductivity and alkaline stability of QPVA_1-X%-(B-C)_X% AEMs can be effectively optimized by precisely adjusting the amount of B-C added. Among them, the membrane with 30 wt% B-C content exhibits the highest OH⁻ conductivity, reaching 95.31 mS·cm^-1 at 80 °C. Notably, it also demonstrates limited swelling, with a swelling ratio of 60.06%, and excellent alkaline stability. Specifically, after being immersed in 2 mol·L^-1 KOH solution at 30 °C for 168 h, the OH⁻ conductivity of the QPVA_70%-(B-C)_30% AEM remains at 83.80% of its original value. Moreover, the membranes demonstrate outstanding mechanical properties, registering a tensile strength of 27.54 MPa and an elongation at break of 156.25%. A single cell incorporating the QPVA_70%-(B-C)_30% AEM attains a peak power density of 469 mW·cm^-2 at 80 °C. These results indicate that the membranes engineered through the rigid-flexible crosslinking strategy hold significant application potential in AEMFCs.